Why Donald Trump is going 'birther' on Ted Cruz

Echoing his false assertions about President Obama's birthplace, Donald Trump has described fellow GOP presidential contender Ted Cruz's Canadian birth as a 'very precarious' problem.

Mark Kauzlarich (left) and Brian Snyder (right)/Reuters/Files

A combination photo shows U.S. Republican presidential candidates Donald Trump in Lowell, Mass., and Ted Cruz in Boone, Iowa, both on Monday. Republican presidential front-runner Donald Trump has waded back into the topic of eligibility for the US presidency, telling the Washington Post that rival Ted Cruz could run into trouble if he won the party's nomination because he was born in Canada.

Now, the Republican presidential candidate is targeting 2016 rival Ted Cruz, suggesting the Texas senator's Canadian birth could be a "very precarious" problem.

"Republicans are going to have to ask themselves the question: 'Do we want a candidate who could be tied up in court for two years?' That'd be a big problem," Mr. Trump told the Washington Post Tuesday. "It'd be a very precarious one for Republicans because he'd be running and the courts may take a long time to make decision. You don't want to be running and have that kind of thing over your head."

“I’d hate to see something like that get in his way," Trump added. But a lot of people are talking about it and I know that even some states are looking at it very strongly, the fact that he was born in Canada and he has had a double passport.”

While the two have had a relatively friendly relationship in this race, the comments come less than a month before voters begin caucusing in Iowa, where Sen. Cruz has passed Trump in most polls. Cruz appears to be doing well with evangelical voters who are a critical voting bloc in the Hawkeye State's caucuses, which may be why Trump is turning up the volume on his attacks. Last week he questioned Cruz's evangelical faith, telling a crowd of supporters, "In all fairness, to the best of my knowledge, not too many evangelicals come out of Cuba, OK?"

The US Constitution requires the president be a "natural-born citizen."

Cruz was born in Calgary, Canada, in 1970, but was automatically granted American citizenship at birth because his mother was an American citizen who had lived in the United States. (His father was Cuban-born.) He held dual citizenship with the United States and Canada until he renounced his Canadian citizenship in May 2014.

Most legal experts agree Cruz meets constitutional criteria, but, as PolitiFact noted last year, the issue is not completely resolved because the Supreme Court has never weighed in on such an issue.

Interestingly, Trump has acknowledged this in the past. In an interview with ABC News in September, he said, "I hear it was checked out by every attorney and every which way and I understand Ted is in fine shape."

For his part, Cruz is laughing off the attack with a veiled jab of his own.